Network resilience is becoming a key issue in the design of IP-based multimedia and multiservice networks. The current discussion about IP network resilience centers around MPLSbased recovery mechanisms. Any well designed recovery strategy has to take into account the different resilience requirements of the single traffic flows in order to avoid excessive usage of bandwidth for standby links. Faced with multiple recovery options, an ISP or NSP must decide which flows to protect to what extent against network failures. In this article an extension to existing Quality of Service (QoS) architectures is presented that integrates the signaling of resilience requirements with the traditional QoS signaling. We refer to this extended QoS model as Resilience-Differentiated QoS (RD-QoS). At the border of MPLS domains, the resilience requirements can then be directly mapped to the appropriate MPLS recovery options. A traffic engineering process for the provisioning of the resilience classes is introduced, and a case study demonstrates the significant network capacity savings achievable via this approach.

The availability requirements for today's networks are very high. Higher availability often comes with a higher cost. We describe several steps required for estimating the costs of realistic network scenarios. Capital expenditures (CapEx) and operational expenditures (OpEx) are classified. An activity-based approach is used to quantify the cost of the event-driven operational processes such as repair and service provisioning. We discuss activity duration and availability parameters as required input data, which are necessary for calculating the processes' costs for realistic network scenarios. The relevant availability measures for an IP-over-Optical network are described using a triplet representation with optimistic, nominal, and conservative values. The model is applied to a reference German network scenario.

Quality of service issues of IP networks are mostly related to guaranteeing bandwidth for flows. However, many interactive real-time applications also require this bandwidth in an uninterrupted fashion. The paper describes how multipath routing and local failure reaction can be employed to provide uninterrupted QoS to applications. We show how multipath route sets can be found in reasonably meshed networks and how multipath routing can be used to save on the spare capacity required in case of link failures

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In this paper we present a novel approach to assess the impact of new and existing services on traffic volume in current and future backbone networks. Several proposals to model traffic load in access and backbone networks exist in the literature. These proposals consider current Internet traffic like http, smtp, ftp and Peer-to-Peer (P2P). We expect, however, that there will be a change in traffic load for future networks caused by services like IP Television (IPTV), Video on Demand (VoD) and Virtual Private Networks (VPN). Additionally, population-based models may no longer be applicable due to the widespread use of service-providers and hierarchical routing through network peering points. Therefore, it is important to reassess future traffic volumes and traffic patterns and to identify those services that have the most impact on the networks. We model today's traffic volume of each of the described services and estimate future traffic volumes taking peering points into account. To illustrate the different traffic flows and to characterise the traffic distribution we apply our results to a Germany reference network.